A Quantitative and Statistical Method of γ'Precipitates in Superalloy Based on the High-Throughput Field Emission Scanning Eelectron Microscope
Superalloys are used widely in national defense,energy,maritime,aviation,and other vi-tal areas requiring stable and reliable materials owing to their excellent oxidation and heat corrosion resis-tance,high-temperature strength,good fatigue performance,and fracture toughness.The presence of a coherent gamma prime(γ')precipitate is the main factor affecting the high-temperature mechanical prop-erties.Therefore,obtaining the quantitative and statistical γ'precipitate data is indispensable for examin-ing and developing new superalloys.On the other hand,conventional instruments and methods barely achieve this goal.In this study,high-throughput field emission scanning electron microscope(high-throughput SEM)was introduced because of its high-speed imaging and original position visualization.Based on the high-throughput SEM,an innovative deformation GH4096 superalloy prepared at five differ-ent solution cooling rates were used as an object to establish a quantitative and statistical method for characterizing the primary,secondary,and tertiary γ'precipitates.Many images of γ'precipitates with magnifications of×57000 and×3000 were obtained rapidly,and methodologies for recognizing the γ'pre-cipitates were developed using MIPAR software.Matrices of images of different amounts were formed.Through these methodologies,information on these matrices was obtained,including the ratio of the pri-mary γ'precipitates area fractions between images with magnifications of×57000 and×3000.The ratio between the amounts of secondary and tertiary γ'precipitates and the area fraction of the secondary and tertiary γ'precipitates varied with the number of images investigated,respectively.By comparing the ten-dencies of these three results,the minimum field of view that could represent the actual distribution of γ'precipitates was set to a matrix of 13×13 images with a magnification of×57000 and a pixels square of 2048×2048.Considering the consistency between the results of the standardized small-angle X-ray scattering(SAXS)and γ'precipitates in the 13×13 images,the established method was quantitative in characterizing the primary,secondary,and tertiary γ'precipitates of GH4096 superalloy.The results of the samples with five different solution cooling rates showed that the solution cooling rates strongly influenced the morphology and quantitative results of the γ'precipitates.Moreover,the behavior of the precipitates corresponded to the classical nucleation growth mechanism and Ostwald Ripening.The solution cooling rates influenced the tensile strength of the samples.The samples exhibited excellent tensile strengths at relatively faster cooling rates,more secondary γ'precipitates,and a higher total area fraction of secondary and tertiary γ'precipitates.Overall,a GH4096 superalloy was prepared using the established method.The statistical and quantitative results of the γ'precipitates highlight a novel way of studying the impact of the solution cooling process on γ'precipitates that can predict the performance of GH4096 superalloys.
GH4096 superalloynanoparticleγ'precipitatehigh-throughput field emission SEMim-age analysischaracterization region
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